The population that uses Active Directory lives almost exclusively on Windows.

The population that uses FCP lives almost exclusively on MacOS (OSX is dead, long live OSX)

The population that uses Docker does not live exclusively on Linux. In fact, a minority of developers works on Linux laptops, even when they target it for deployment. It's a larger minority than in other sectors, but it's definitely a minority, not even a relative majority. The population of (web) developers is possibly the most evenly-distributed of all, in terms of OS.

If someone was trying to run FCP on an OS X VM on a linux box, what would you tell them?

It's not the fault of docker or linux containers that people insist on trying to use the technology on another unsupported operating system.

Obviously, it's the fault of people - as I said in the comment above: I'm surprised it got so popular among people, considering how much it sucks on the platforms lots of them use.

The whole idea of using Docker for dev boxes is to eliminate the cross platform dependency issues and make it easier for everyone, without maintaining wikis for each OS version. We don't use Docker at work because of the non-Linux performance issues.

Running the docker daemon in a linux VM on your OS X system and then complaining about performance is silly.